The switch to digital is putting most projectionists out of work. But without supervision, digital projection can go wrong in many of the ways film projection can, and also in ways it can't, leaving theater managers and moviegoers frustrated with dimness, glitches, and out-and-out absurdity (picture a Windows task bar across the bottom of the screen for the length of a movie, and you get the idea).

What we see on a motion-picture screen is, of course, subject to a lot of variables apart from projection, like cinematography and lighting. When it comes to digital, add in issues like compression level, resolution, and resampling. And of course, personal taste. But certainly there's no reason a multi-million dollar studio production in 2012 shouldn't pop off the screen.

Last year, in a front-page article in the Boston Globe and a follow-up blog post, Globe movie critic Ty Burr sparked a national debate by decrying an epidemic of dimness in local projection, putting particular emphasis on the digital projection at the AMC Loews Boston Common 19-plex downtown. Roger Ebert took up the cause, writing a lengthy and emotional blog post affirming the problem of projection dimness as a national one. Sony, whose 3D projectors were Burr's whipping post, felt the need to issue a point-by-point rebuttal of the claims.

Burr's article was a "flashpoint" for AMC Loews Boston Common, says Ryan Noonan, AMC's director of public relations, "part of a larger transition" to digital.

Perhaps to show off the end result of that anticipated transition, a team of AMC managers and executives recently gave a tour of the Boston Common projection booths to a small group of local journalists, including myself. We met in the lobby at 9 am on a recent Monday and were led upstairs and into the cinema's back chambers. The projection booths were massive. They looked like a storage closet on the alien ship in Prometheus — long, deserted caverns inhabited by motionless and surprisingly large black boxes with Sony logos on their butts.

Toward the end of our tour, Erik Gomez, the Boston Common's newly hired presentation quality cop, led me out of one of these rooms into an empty theater to show me how he measures screen light levels. Standing next to me at the back of the room, he pointed a handheld light meter at the center of the all-white image on the screen. The meter's digital readout promptly ticked up above 14 foot-lamberts, the standard brightness value set by the Society of Motion Picture and Television Engineers. The bottom third of the screen was noticeably dimmer than the center, however. I asked him to point the light meter there, and the reading dropped to 11 foot-lamberts.

Projectionists I spoke with told me that a large area of the screen being visibly dimmer during a light check is definitely a problem, and a fixable one — though not necessarily an easily fixable one. Getting light to be bright and even across all parts of the screen can be a painstaking, iterative process of lens-and-bulb focus adjustment.